80af3007 ​

let yn: Int
let xn: Int
let y: Int
let x: Int
let g: OList OList Color

let input = fill yn (fill xn black)
  |> grid (y, x) (gmapg (λc. fill 3 (fill 3 c)) g)

let output = gmapg (λc. if (c == black) (fill 3 (fill 3 black)) g) g